Re: [dpdk-dev] [PATCH v3 3/3] test/power: add delay before checking cpuinfo cur freq

[Liang Ma <liangma@liangbit.com>]

On Thu, Apr 08, 2021 at 05:16:34AM +0000, Richael Zhuang wrote:
> Hi Liang,
> Sorry that last email contains "confidential notice", so I resend it.
> > -----Original Message-----
> > From: Liang Ma <liangma@liangbit.com>
> > Sent: Wednesday, April 7, 2021 6:15 PM
> > To: Richael Zhuang <Richael.Zhuang@arm.com>
> > Cc: dev@dpdk.org; alan.carew@intel.com; stable@dpdk.org; David Hunt
> > <david.hunt@intel.com>; Pablo de Lara <pablo.de.lara.guarch@intel.com>
> > Subject: Re: [dpdk-dev] [PATCH v3 3/3] test/power: add delay before
> > checking cpuinfo cur freq
> > On Wed, Apr 07, 2021 at 03:46:36PM +0800, Richael Zhuang wrote:
> > > Sleep for 1s before checking the newly updated value from
> > > "/sys/devices/system/cpu/cpu%u/cpufreq/cpuinfo_cur_freq", because for
> > > some systems it may not be effective immediately.
> > >
> > > Fixes: ed7c51a6a680 ("app/test: vm power management")
> > > Cc: alan.carew@intel.com
> > > Cc: stable@dpdk.org
> > >
> > > Signed-off-by: Richael Zhuang <richael.zhuang@arm.com>
> > > ---
> > >  app/test/test_power_cpufreq.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/app/test/test_power_cpufreq.c
> > > b/app/test/test_power_cpufreq.c index cda74bd8a..7a93bc90a 100644
> > > --- a/app/test/test_power_cpufreq.c
> > > +++ b/app/test/test_power_cpufreq.c
> > > @@ -47,6 +47,9 @@ static uint32_t
> > freqs[TEST_POWER_FREQS_NUM_MAX];
> > > static int  check_cur_freq(unsigned lcore_id, uint32_t idx)  {
> > > +/* wait for the value to be updated */
> > > +sleep(1);
> > Hi Richael,
> >   1 second looks way too much for CPU frequency  swap.
> >   The unit should be ms in the worst case regardless the vendor, IMO.
> > Regards
> > Liang
> Thanks for review. Although I also think this time seems too long,
> it needs more than 700ms when I tested on our arm platform.
Hi Richael, 
   I will suggest you talk with arm cpufreq driver maintainer(kernel). 
   I don't think HW need 700ms to complete frequency changes. 
   cpufreq driver might do something here. intel_pstate driver set the
   threshold as 10ms, according to the kernel source code.  
Regards
Liang
> > > +
> > >  #define TEST_POWER_CONVERT_TO_DECIMAL 10
> > >  FILE *f;
> > >  char fullpath[PATH_MAX];
> > > --
> > > 2.20.1
> > >
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